398 SELIG HECHT 



for all species, being situated at 36 per cent of the length behind 

 the snout." 



In striking contrast to the similarities shown by the other 

 ratios, the values for the depth-constant vary considerably. A 

 comparison of these with the weight-length constant, given in 

 table 2, shows that, in general, a species having a high value for 

 the depth constant has also a high value for the weight-length 

 constant (e.g., Peprilus alepidotus) and vice versa (e.g., Anchovia 

 brownii). It would therefore seem that the 'special' form of a 

 fish, as contrasted with the generalized fish-form, is largely 

 determined by its depth measurement. 



SUMMARY 



1. From the study of eleven species of fish, representing seven 

 families, it has been shown that, in all of them, weight and 

 length are closely correlated. This relation is such that weight 

 is equal to a constant multiplied by the cube of the length: — 



weight = a X (length) ^ 



2. The factor a serves as a convenient index of the 'condition' 

 of the fish at different seasons of the year. 



3. Sex has no influence on these correlations. 



4. In all the species, measurements of the selected external 

 body parts are simple linear functions of length, and are constant. 



5. A relationship is shown to exist among weight, length, 

 width, and depth, such that the value of weight may be expressed 

 in terms of the other three. The equation is 



weight = K X length X depth X width, 



in which K varies but little from species to species, and repre- 

 sents in each a modified value of the specific gravity. 



6. The rates of growth of the different selected parts of the 

 fish are identical. 



7. Comparison with other data indicates that in animals hav- 

 ing an indeterminate growth, the external form is established 

 early in the post-embryonic life of the individual, and is adhered 

 to, within rather narrow limits, for the rest of its life; whereas 



